Field of the Invention
The invention relates to rotary cutting tools with cutting inserts mounted thereon, and in particular to a milling cutter with helical cutting inserts that can be reground while mounted on the cutter body to provide a smooth cut on the workpiece.
Description of Related Art
One of the current concerns in indexable finish style milling is the stepped or wavy surface on the milled surface resulting from current technology, specifically in the areas of face and end milling. This stepped, uneven or otherwise irregular finish is typically a result of the type, position and location of the cutting inserts. This stepping is particularly relevant in attempts at all-in-one mills, that is mills capable of three dimensional milling, including plunging, ramping, circle interpolating, facing, and end milling with the same mill.
Cutting inserts that are not properly aligned along the flutes of the milling cutter will provide such stepping. For example, on helical milling cutters the inserts must be aligned to follow the curved contour of the helix and any misalignment results in stepping or other irregular finish such as a groove or lip where one insert is radially outward further than adjacent inserts. In addition, cutting inserts that have substantially rectangular configurations (that is, with long, flat cutting edges) will provide such stepping. This stepping is caused by the rectangular configuration of the insert removing excessive material from the workpiece at or approaching the corners of the inserts thereby causing stepping. In contrast, cutting inserts that have an arc-like periphery along its entire cutting surface (radiused corners that extend across the whole cutting edge) remove excess material from the workpiece along the mid-section of the cutting insert, thereby causing valleys.
According to the milling users, this stepped surface is often unacceptable, particularly when a finished, not rough, flat surface is desired. This stepping is unacceptable because stress points form at each or some of the inner and outer edges of the steps as these edges are often well defined. This forces the milling user to thereafter finish mill the surface that is an additional time consuming and expense-adding step.
Such improvement continues to be sought by mill users in various industries because such reduction or complete elimination of all stepping and waviness will increase the overall life of the metal end product by reducing and/or eliminating stress, fatigue and other undesirable forces working against the metal end product. In conjunction with this, if such milling cutter could perform all or substantially all of the typical milling steps including ramping, plunging, circle interpolation, facing and end milling, then significant cost and time reduction would also be achieved. Finally, if all such milling steps could be achieved by one milling cutter, the cutter must have a reasonable life as these various steps involve different concerns and factors including the subjecting of the cutter to large axial, radial, and tangential forces, possibly simultaneously.